Hi Don,
I removed, checked, cleaned and reinserted T6 and T7. I also did a visual
check for bad joints around Q21.
I also did a side by side comparison with my FT-897 while listening in to a
LSB QSO on 40m. The same antenna was used and I switched between radios
using a B&W switch. Without the preamp on, the K2 exhibited better signal to
noise ratio than the FT-897 with the preamp running. The K2 preamp, when
engaged, amplified both noise and signal with no further improvement in
quality.
When the K2 preamp is switched in, the S-meter will jump from S1-S2 to +20dB
(on 20m, untuned antenna). This seems to be rather large and I'm wondering
if the preamp is working fine, but one of the other amps is faulty. I'm
going to give the IF and post-mixer amps a good look later today.
Thanks,
Kathy
----- Original Message -----
From: "Don Wilhelm" <[EMAIL PROTECTED]>
To: "K.Kishimoto" <[EMAIL PROTECTED]>; <[email protected]>
Sent: Monday, December 26, 2005 3:20 PM
Subject: RE: Other questions was RE: [Elecraft] K2 Alignment and Test,Part
III: High current
Kathy,
Great that you found the transmit problem - and if you can use larger wire
for the power supply, the voltage drop will be less and will likely reduce
your current draw on transmit a bit more.
Yes, your preamp dropout problem does sound like a bad solder connection
is
the most likely cause. Places to check are those components associated
with
Q21 - look on the schematic (sheet 2) for the RF Board to identify those
associated components, and don't overlook pins 4 and 7 of relay K17 and
toriod T6. Actually anything in the receive chain from the antenna
through
the IF Amp will effect the AGC action (and subsequently the S-meter), but
if
the S-meter appears normal with the Preamp off, then the problem is likely
confined to the preamp stage.
Solve the preamp problem first and then tackle the AGC - since your
S-meter
seems close to normal with the preamp off, fixing the preamp may take care
of the S-meter anomoly too. True the AGC (and S-meter) should not behave
as
you describe, but you can optimize the AGC threshold after you know
everything else is working properly, then finally adjust the S-meter as
the
last step.
73,
Don W3FPR
-----Original Message-----
Hi Don and everyone else who responded,
The current readings @ 5W and 10W are now at the upper end of
normal levels.
T4 was reversed and needed to be turned around. The power wire is also on
the thin side, 16g or 18g. I'll find a replacement tomorrow.
Two new interesting problems have cropped up as well:
a) 20m band, tuned Zepp: The S-meter is pegged on +40dB when the
preamp is
on. With the preamp off, the meter settles down to around S5 (S5-S9 when
copying a signal). On 40m, antenna tuned, the LED reads +40dB with preamp
and +20dB without. Tried following the S-meter setup instructions in the
manual, including those on the XG1 mini-kit, but nothing seems to prevent
the LED from locking into the upper limit when the preamp is on. Is this
normal? The AGC can be switched on and off as well as set fast or
slow. With
AGC off, the S-meter drops to zero.
b) The gain drops intermittently from an S-meter reading of +40dB
to S2 with
preamp on. The audio also diminishes in intensity at the same
time. The last
time it did this, I tapped the left side of the radio a couple of
times and
it stopped dropping out. This sounds like a loose component, bad
connection
or bad solder joint. Where should I begin my search? The IF
stage? Could it
be a toroid with a bad solder joint?
Thanks,
Kathy
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